Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to cyclic redundancy check (CRC) false detection reduction in communication systems.
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
In some wireless communication networks, inefficient and/or ineffective utilization of available communication resources, particularly related to error detection, may lead to degradations in wireless communication. Even more, the foregoing inefficient resource utilization inhibits user equipments and/or wireless devices from achieving higher wireless communication quality.
For example, W-CDMA systems provide data services using transmission links and associated protocols. At a receiving entity (e.g., a user equipment) in a W-CDMA system, the channel format of a block of data sent by a transmitting entity (e.g., a base station) has to be correctly identified and the overhead and payload in the data have to be correctly decoded to enable proper operation of the system. Some coding schemes are described in detail in 3GPP Standard Technical Specification (TS) 25.102. An example coding scheme for the receiving entity is blind transport format detection (BTFD) for detecting the format of transport channels, and, in particular, for detecting an end of a block of data for a channel. This is based on the information that the block may be terminated by an error detection code, e.g., a cyclic redundancy check (CRC) code. The BTFD mechanism uses the information that the block is terminated by a CRC code to determine whether a given sequence of bits is a CRC code for a block of data (bits) preceding the CRC code (bits). For example, explicit BTFD may involve performing recursive Viterbi decoding followed by CRC checks. When a CRC pass is detected, state variables are updated and the resulting decoded bits are passed to the upper protocol layers. However, in some instances, the recursive decoding may result in a false CRC pass where the detected transport format was not actually transmitted.
For example, CRC bits may help ensure that a receiving entity decodes a grant message correctly when the grant message was actually sent by the transmitting entity. However, this may not be enough to stop the receiving entity from falsely detecting a grant message when no grant message was sent by the transmitting entity or another type of message was sent by the transmitting entity. The receiving entity, in some cases, may decode bits that may match valid CRC bits, resulting in the receiving entity detecting a false grant message, referred to as “ghost grants.” The upper protocol layers of the receiving entity may treat the ghost grants as a valid grant (e.g., genuine or valid packets received from the physical layer) which may affect performance of the UE and/or the network, e.g., dropped voice calls. Additionally, as grant messages (e.g., absolute grant messages) indirectly control the uplink (UL) power level, false detection of a grant message negatively affects network capacity and/or receiving entity throughputs. For example, a false grant message may set the receiving entity transmit power at a level different from the level intended by the transmitting entity, e.g., a serving base station or cell, and may cause interference with other entities (e.g., other UEs or cells).
Therefore, there is a need for improved methods of signal detection for reducing the occurrences or probability of false detection of data sent by a transmitting entity.